A. Field of the Invention
This invention relates to an ophthalmological instrument capable of measuring intraocular pressure of an eye to be tested and the radius of curvature of the cornea of the eye in a noncontact manner.
B. Description of the Related Art
A tonometer for measuring intraocular pressure of an eye to be tested in a noncontact manner is disclosed in, for example, Japanese Patent Publication No. Sho 54-38437, Japanese Patent Application No. Sho 59-242279, or Japanese Patent Publication No. Sho. 62-30768.
The device of Japanese Patent Publication No. Sho 54-38437 is designed such that an air pulse as a fluid is discharged toward the cornea of an eye to be tested in accordance with a known pressure-time function and the applanation state of the cornea is photoelectrically detected to measure a period of time starting from the discharge of an air pulse (sometimes referred to as "air puff") to the applanation of the cornea in order to measure intraocular pressure of the eye.
The device of Japanese Patent Application No. Sho 59-242279 is designed such that an air pulse is discharged to the cornea of the eye to detect pressure of the discharging air pulse, a quantity of reflected light from the cornea is photoelectrically detected with reference to the pressure as a parameter, and the intraocular pressure is determined by such a device when the cornea is transfigured by a predetermined amount.
The device of Japanese Patent Publication No. Sho 62-30768 is designed such that an air current of a predetermined pressure is projected to the cornea, a light flux irradiates the cornea, and the intraocular pressure is measured in accordance with varied quantity of the light flux reflected by the cornea before and after the air current is projected to the cornea.
On the other hand, corneal configuration measuring device for measuring the radius of curvature of the cornea of the eye to be tested, is disclosed in Japanese Patent Application No. Sho 61-102800 and Japanese Patent Application No. Sho 61-310009. The devices disclosed in these publications are designed such that a ring pattern is projected to the cornea of the eye through an objective lens facing the eye, an image thereof reflected by the cornea is received by a two-dimensional detecting element, such as an area CCD, and the radius of curvature of the cornea are measured from the configuration of the pattern.
As seen above, heretofore, the measurement of intraocular pressure of the eye and the measurement of the radius of curvature are separately effected using separate devices such as a noncontact type tonometer (hereinafter referred to as the "tonometer") and a corneal configuration measuring device (hereinafter referred to as the "keratometer").